Contact Mismatch Error

All of a sudden, I'm having an issue with my IP Phone.. It connects to my PBX and can make incoming and outgoing calls. I have the 3CX client for windows on my laptop, and I also have the app on my iphone... Once I go to the App on my iphone, my IP phone goes into no service. When I go into the WebGui and see the status it says Contact Mismatch Error. I reboot the Phone, If the App is still on, I get this same error. If the App is off, phone boots right up, but as soon as I go into the app, get the same thing. I do not get this error on the 3CX client for windows on my laptop, just the app on my iphone. I uninstalled the app from the iPhone. I did another send e-mail of the config files, and still the same thing. I never has this issue before, and now all of a sudden, I am. There was nothing that has changed since the config and provision of these 2..

I would first check the 3CX Activity log to see what is happening during registration of both devices. Any obvious error messages? Two or more devices, using the same extension number, registering at the same time, is SIP Forking, which is supported by 3CX, and should work with no issue. The log should show if there is something else, with the iPhone, going on.

Does the issue occur on..... 3/4G, Wifi hotspot, Wifi on the local LAN?

Looked at the event long in the dashboard... Nothing unual... Just a registered and unregistered... But what was interesting. I dumped the phone and re-booted to factory Defulats, and then started from scratch. And it worked.. But now 24 hours later. Back to the same issue... I still don't know the issue either...